This proposal is designed to identify the interrelationship between stress and spinal cord oxytocin (OT) and vasopressin (VP) in spontaneously hypertensive rats (SHR). Our preliminary results with Long Evans rats have demonstrated that immobilization stress significantly increases spinal cord OT and VP while decreasing pons-medulla OT. Our preliminary results have also demonstrated lower VP contents in the spinal cord of 12 weeks old SHR when compared with age matched Wistar Kyoto (WKY) rats. Now we wish to determine whether SHR and WKY rats respond similarly in changing spinal cord VP, and perhaps OT, following an application of immobilization stress. Also, hypertonic saline, exercise and hypovolemic stressors will be applied to SHR to determine the correlation of each of these stressors with the levels of the spinal cord OT and VP. Hormones will be estimated primarily by radioimmunoassay in pituitary, hypothalamus, pons- medulla and spinal cord samples. Experiments are designed to determine whether chronic stress attenuates changes in spinal cord OT, VP contents. Furthermore, whether catecholaminergic or endogenous opioid peptides are involved in stress-induced changes of spinal cord OT and VP levels will be evaluated. The proposed studies should help to elucidate the role of spinal cord OT and VP in stress. The new information is expected to help us to better understand the etiology of hypertension in this animal model (SHR).